The present invention relates to an electron microscope that uses a method by which observation result of a sample is stored as image data, and more particularly to an electron microscope that is suitable for use in repetitive observation of the same sample.
In observation of a sample using an electron microscope, it is necessary to set observation conditions such as magnification, acceleration voltage of an electron beam, and an observation mode, which are suitable for observation of the sample, before starting the observation.
In this case, these observation conditions are set by devices that are generically called observation-condition setting devices such as a device for controlling an electron gun, a device for controlling an irradiation lens, a device for controlling an objective lens, a device for controlling a magnifying lens system, and a device for controlling a sample stage.
These observation conditions are a part of information that is indispensable to evaluation of the observation result of the sample. Therefore, when saving an image, it is desirable to save observation conditions of the recorded image together with the image.
In this connection, when recording the observation result obtained by the electron microscope as an image, either of the following methods is generally conventionally used: a method in which the observation result is saved in an image recording medium, such as a photographic film, as a real image: and a method in which the observation result is saved in a memory as image data by a TV camera (Television Camera).
With both of the methods described above, it is possible to record the observation conditions together with the recorded image. However, if the observation conditions are recorded on a film, it is difficult to record all observation conditions because a writing area is limited. On the other hand, in the case of the image data by a TV camera, there is no hard problem of a writing area. Therefore, the observation conditions can also be displayed immediately in real time together with the image.
In the prior art, for example, while observing a certain sample, if the observation is interrupted for some reason, but an operator tries to start the observation again, the following operation is required: displaying observation conditions together with an image using the recording method for image data; and while watching the displayed observation conditions, providing an electron microscope with each condition setting by manual operation with reference to the observation conditions.
The prior art described above has a problem in work efficiency because settings of the observation conditions when restarting the observation are not taken into consideration.
As described above, when using an electron microscope, it is necessary to set desired observation conditions in response to a sample to be observed. This requires considerably complicated work.
The reason why complicated work is required for the settings of the observation conditions is that as described above, the observation conditions cover a wide variety of conditions: that is to say, in addition to magnification and acceleration voltage, there are many observation modes including, for example, a diffraction mode, a high resolution mode, a high contrast mode, and an extremely low magnification mode.
When starting observation of a certain sample, it is natural that complicated work is required. In other words, it is unavoidable. However, in the prior art, even if the same sample is observed, settings of the observation conditions by manual operation is required for each observation-condition setting device every time the work is started. This causes work efficiency to be decreased.